The present disclosure relates to a semiconductor device, and a method for fabricating the same, particularly to a semiconductor device including a metal insulator semiconductor field-effect transistor (MISFET) having a gate insulating film including a high dielectric constant film, and a method for fabricating the same.
For higher performance of semiconductor integrated circuits, a gate insulating film made of a high dielectric constant material, typically alumina (Al2O3), hafnium oxide (HfO2), and hafnium silicate (HfSiOx), has been taking the place of a conventional gate insulating film made of a silicon oxide film or a silicon oxynitride film. Further, a full-metal gate electrode made of a metal film, or a gate electrode constituted of a metal-inserted polysilicon stack (MIPS) having a metal film inserted between a gate insulating film and a polysilicon film has been taking the place of a conventional gate electrode made of a polysilicon film.
Threshold voltages of an n-type MISFET (hereinafter referred to as an n-type MIS transistor), and a p-type MISFET (hereinafter referred to as a p-type MIS transistor) can be controlled by using gate electrodes having metal films made of metal materials different from each other in the n-type MIS transistor and the p-type MIS transistor. When an MIS transistor has a gate insulating film including a high dielectric constant film, and a gate electrode including a metal film, the threshold voltage of the MIS transistor can be controlled based on a work function of the metal material of the metal film in the gate electrode.
However, the above method has the following demerits. For example, since the materials of the gate electrodes of the n-type and p-type MIS transistors are different, the gate electrodes of the n-type and p-type MIS transistors need to be formed separately, which complicates fabrication steps. Further, a margin (an allowance) of an N/P boundary region between the n-type and p-type MIS transistors needs to be increased, thereby making densification and miniaturization of the n-type and p-type MIS transistors difficult.
According to another method for controlling the threshold voltages of the n-type and p-type MIS transistors, the gate electrodes of the n-type and p-type MIS transistors are made of the same material. A gate insulating film including a high dielectric constant film containing lanthanum (La) is used in the n-type MIS transistor, and a gate insulating film including a high dielectric constant film containing aluminum (Al) is used in the p-type MIS transistor (see, e.g., Non-Patent Document 1: Hyung-Suk Jung et al., “A Highly Manufacturable MIPS (Metal Inserted Poly-Si Stack) Technology with Novel Threshold Voltage Control,” VLSI Tech. Digest 2005, and Non-Patent Document 2: H. N. Alshareef et al., “Thermally Stable N-Metal Gate MOSFETs Using La-Incorporated HfSiO Dielectric,” VLSI Tech. Digest 2006).
The above method is advantageous because has the following merits. For example, the fabrication steps are simple because the gate electrodes of the n-type and p-type MIS transistors are made of the same material. Further, the gate electrodes can easily be processed.